A proposed Shared Instrument Grant (SIG) is submitted for a one-time award to upgrade the existing Bioengineering laser Doppler velocimetry (LDV) system to a state-of-the-art, three-component fiber optic system including multi-axis computer controlled traversing capabilities. The existing two-component system in the Bioengineering Program is 17 years old, and has been used extensively on numerous NIH funded projects throughout this period. The current system is outdated, and beyond a state of repair due to hardware no longer supported by the manufacturers. The proposed facility will replace the current obsolete system and upgrade Bioengineering's LDV capabilities. Laser Doppler velocimetry is considered to be the gold standard velocity measurement technique in the biomedical field. As a result, numerous (including NIH supported) projects have relied on the Bioengineering Program's system to provide accurate flow field quantitation in the area of bio-fluid mechanics. The specific aim of this SIG proposal is to upgrade Bioengineering's LDV system to a semi-portable, fiber-optic based system (including multiple-axes and automated traversing) that can be shared among the different investigators requiring bio-fluid mechanical measurements. The system will incorporate the current state-art-of-the-art in signal processor technology, fiber-optic versatility with multiple receiving capability. The multi-axis traversing system will be designed around an optical rail based system to provide versatility in traversing hardware set-up. Thus, each investigator can tailor the traversing system to their flow loop geometry and maximize efficiency and optical access. The instrumentation facility will find immediate and future use in studies focusing on vascular engineering, cardiovascular fluid mechanics, biomedical instrumentation technology, flow related investigations of the pulmonary system and cellular transport. The system will provide a gold standard velocity measurement for NIH funded research and the NIH training center for Medical Ultrasonic Transducer Technology. The system will be the primary measurement system for the ongoing research in cardiovascular prosthetics including mechanical heart valve cavitation and ventricular assist devices.